'\"
'\" Generated from file 'machineparameters\&.man' by tcllib/doctools with format 'nroff'
'\" Copyright (c) 2008 Michael Baudin <michael\&.baudin@sourceforge\&.net>
'\"
.TH "tclrep/machineparameters" n 1\&.0 tcllib "tclrep"
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.SH NAME
tclrep/machineparameters \- Compute double precision machine parameters\&.
.SH SYNOPSIS
package require \fBTcl  8\&.4\fR
.sp
package require \fBsnit \fR
.sp
package require \fBmath::machineparameters  0\&.1\fR
.sp
\fBmachineparameters\fR create \fIobjectname\fR ?\fIoptions\fR\&.\&.\&.?
.sp
\fIobjectname\fR \fBconfigure\fR ?\fIoptions\fR\&.\&.\&.?
.sp
\fIobjectname\fR \fBcget\fR \fIopt\fR
.sp
\fIobjectname\fR \fBdestroy\fR
.sp
\fIobjectname\fR \fBcompute\fR
.sp
\fIobjectname\fR \fBget\fR \fIkey\fR
.sp
\fIobjectname\fR \fBtostring\fR
.sp
\fIobjectname\fR \fBprint\fR
.sp
.BE
.SH DESCRIPTION
The \fImath::machineparameters\fR package
is the Tcl equivalent of the DLAMCH LAPACK function\&.
In floating point systems, a floating point number is represented
by
.CS


x = +/- d1 d2 \&.\&.\&. dt basis^e

.CE
where digits satisfy
.CS


0 <= di <= basis - 1, i = 1, t

.CE
with the convention :
.IP \(bu
t is the size of the mantissa
.IP \(bu
basis is the basis (the "radix")
.PP
.PP
The \fBcompute\fR method computes all machine parameters\&.
Then, the \fBget\fR method can be used to get each
parameter\&.
The \fBprint\fR method prints a report on standard output\&.
.SH EXAMPLE
In the following example, one compute the parameters of a desktop
under Linux with the following Tcl 8\&.4\&.19 properties :
.CS


% parray tcl_platform
tcl_platform(byteOrder) = littleEndian
tcl_platform(machine)   = i686
tcl_platform(os)        = Linux
tcl_platform(osVersion) = 2\&.6\&.24-19-generic
tcl_platform(platform)  = unix
tcl_platform(tip,268)   = 1
tcl_platform(tip,280)   = 1
tcl_platform(user)      = <username>
tcl_platform(wordSize)  = 4

.CE
The following example creates a machineparameters object,
computes the properties and displays it\&.
.CS


     set pp [machineparameters create %AUTO%]
     $pp compute
     $pp print
     $pp destroy

.CE
This prints out :
.CS


     Machine parameters
     Epsilon : 1\&.11022302463e-16
     Beta : 2
     Rounding : proper
     Mantissa : 53
     Maximum exponent : 1024
     Minimum exponent : -1021
     Overflow threshold : 8\&.98846567431e+307
     Underflow threshold : 2\&.22507385851e-308

.CE
That compares well with the results produced by Lapack 3\&.1\&.1 :
.CS


     Epsilon                      =   1\&.11022302462515654E-016
     Safe minimum                 =   2\&.22507385850720138E-308
     Base                         =    2\&.0000000000000000
     Precision                    =   2\&.22044604925031308E-016
     Number of digits in mantissa =    53\&.000000000000000
     Rounding mode                =   1\&.00000000000000000
     Minimum exponent             =   -1021\&.0000000000000
     Underflow threshold          =   2\&.22507385850720138E-308
     Largest exponent             =    1024\&.0000000000000
     Overflow threshold           =   1\&.79769313486231571E+308
     Reciprocal of safe minimum   =   4\&.49423283715578977E+307

.CE
The following example creates a machineparameters object,
computes the properties and gets the epsilon for
the machine\&.
.CS


     set pp [machineparameters create %AUTO%]
     $pp compute
     set eps [$pp get -epsilon]
     $pp destroy

.CE
.SH REFERENCES
.IP \(bu
"Algorithms to Reveal Properties of Floating-Point Arithmetic", Michael A\&. Malcolm, Stanford University, Communications of the ACM, Volume 15 ,  Issue 11  (November 1972), Pages: 949 - 951
.IP \(bu
"More on Algorithms that Reveal Properties of Floating, Point Arithmetic Units", W\&. Morven Gentleman, University of Waterloo, Scott B\&. Marovich, Purdue University, Communications of the ACM, Volume 17 ,  Issue 5  (May 1974), Pages: 276 - 277
.PP
.SH "CLASS API"
.TP
\fBmachineparameters\fR create \fIobjectname\fR ?\fIoptions\fR\&.\&.\&.?
The command creates a new machineparameters object and returns the fully
qualified name of the object command as its result\&.
.RS
.TP
\fB-verbose\fR \fIverbose\fR
Set this option to 1 to enable verbose logging\&.
This option is mainly for debug purposes\&.
The default value of \fIverbose\fR is 0\&.
.RE
.PP
.SH "OBJECT API"
.TP
\fIobjectname\fR \fBconfigure\fR ?\fIoptions\fR\&.\&.\&.?
The command configure the options of the object \fIobjectname\fR\&. The options
are the same as the static method \fBcreate\fR\&.
.TP
\fIobjectname\fR \fBcget\fR \fIopt\fR
Returns the value of the option which name is \fIopt\fR\&. The options
are the same as the method \fBcreate\fR and \fBconfigure\fR\&.
.TP
\fIobjectname\fR \fBdestroy\fR
Destroys the object \fIobjectname\fR\&.
.TP
\fIobjectname\fR \fBcompute\fR
Computes the machine parameters\&.
.TP
\fIobjectname\fR \fBget\fR \fIkey\fR
Returns the value corresponding with given key\&.
The following is the list of available keys\&.
.RS
.IP \(bu
-epsilon : smallest value so that 1+epsilon>1 is false
.IP \(bu
-rounding : The rounding mode used on the machine\&.
The rounding occurs when more than t digits would be required to
represent the number\&.
Two modes can be determined with the current system :
"chop" means than only t digits are kept, no matter the value of the number
"proper" means that another rounding mode is used, be it "round to nearest",
"round up", "round down"\&.
.IP \(bu
-basis : the basis of the floating-point representation\&.
The basis is usually 2, i\&.e\&. binary representation (for example IEEE 754 machines),
but some machines (like HP calculators for example) uses 10, or 16, etc\&.\&.\&.
.IP \(bu
-mantissa : the number of bits in the mantissa
.IP \(bu
-exponentmax :  the largest positive exponent before overflow occurs
.IP \(bu
-exponentmin : the largest negative exponent before (gradual) underflow occurs
.IP \(bu
-vmax : largest positive value before overflow occurs
.IP \(bu
-vmin : largest negative value before (gradual) underflow occurs
.RE
.TP
\fIobjectname\fR \fBtostring\fR
Return a report for machine parameters\&.
.TP
\fIobjectname\fR \fBprint\fR
Print machine parameters on standard output\&.
.PP
.SH "BUGS, IDEAS, FEEDBACK"
This document, and the package it describes, will undoubtedly contain
bugs and other problems\&.
Please report such in the category \fImath\fR of the
\fITcllib Trackers\fR [http://core\&.tcl\&.tk/tcllib/reportlist]\&.
Please also report any ideas for enhancements you may have for either
package and/or documentation\&.
.PP
When proposing code changes, please provide \fIunified diffs\fR,
i\&.e the output of \fBdiff -u\fR\&.
.PP
Note further that \fIattachments\fR are strongly preferred over
inlined patches\&. Attachments can be made by going to the \fBEdit\fR
form of the ticket immediately after its creation, and then using the
left-most button in the secondary navigation bar\&.
.SH COPYRIGHT
.nf
Copyright (c) 2008 Michael Baudin <michael\&.baudin@sourceforge\&.net>

.fi
